Method for producing annular parts and use of said method

ABSTRACT

The invention relates to a method for working a strip continuously supplied from a coil, using the same equipment for roll bending, cutting and welding in a single combined machine, such that an end product of the required quality is efficiently produced.

The present invention relates to a method for producing annular or tubular parts according to the preamble of claim 1, particularly a method for cutting, rolling, and welding thin steel strip from a coil, and use of the method.

It is generally known that, in methods for producing tubular, cylindrical, or annular objects from flat or wound starting materials, several complex work steps are necessary, first in order to perform the cutting to the desired starting dimensions, second in order to achieve the desired bending as a sum of several partial bending processes, and third in order to provide the rolled part with a welded longitudinal seam, whereby the finished tubular product is then obtained. An important disadvantage of the known bending methods is that the required shape accuracy often cannot be achieved or can be achieved only with significant mechanical and electronic complexity, even if the entire bending process is divided into several individual bending steps. The known roll bending methods are only conditionally suitable for fully automatic use in production lines, because, particularly in the event of a product change, the machine times, which are already relatively long because of the complex forming processes, are further increased because of tool changes, and thus the economy is further reduced.

Known methods for forming metals sheets are the classic two-roll bending method or the three-roll bending method, also called rolling. A disadvantage of these methods is that different tube diameters require parts of the device—particularly the clamping tools—to be exchanged, whereby the economy of the system also decreases. An invention that avoids the exchange of parts of the device for different tube diameters is described in patent document EP 0 701 878 B1. In this design, flat or tubularly pre-formed metal-sheet blanks are fed to the welding system by means of an additional placement system. The cutting and pre-forming thus occur outside of the described system, which results overall in a greater investment expense and thus has an adverse effect on the investment costs of the entire system.

In patent document DE 10 2008 027 807 B4, a method for producing steel pipes is described, wherein a metal sheet or coil is formed into a tubular body in a bending operation, provided with a longitudinal seam in a subsequent welding operation, and then subjected to a stress-relief treatment.

This method contains complex forming tools having a control device and contains an additional stress-relief treatment for reducing the stresses mechanically produced by the forming of the metal-sheet material. Such a complex method is sensible for thick-walled tubes but is less suitable for thin-walled tubes according to the present invention.

It is apparent that these methods mentioned above are associated with significant complexity. Therefore, the problem addressed by the present invention is that of specifying a method that does not have the disadvantages mentioned above.

This problem is solved by means of the features stated in claim 1. Advantageous embodiment variants are stated in the dependent claims.

The invention presented here describes a method that allows, in a continuous processing process, thin-walled, sheet-shaped starting material to be cut to the desired dimensions in a first sub-process, then to be rolled in a second sub-process, and finally to be provided with a welded longitudinal seam in a third sub-process by means of the same equipment—a combined machine. This results in lower investment costs for machines, and lower variable costs in the operation of such an inventive installation also result, because no tools have to be exchanged during production in the event of changing production batches. Overall, this innovative method results in a favorable cost-benefit ratio for such final products which, on the basis of the tolerances, do not demand very high requirements, for example for drums of washing machines or of dishwashers.

Below, the present invention is explained further on the basis of embodiment examples with reference to drawings.

FIG. 1 shows a schematic illustration of the production of annular parts according to the prior art.

FIG. 2 shows a schematic illustration of the production of annular parts according to the invention.

FIG. 3 shows a first cross-section of a combined machine according to the invention for producing annular parts.

FIG. 4 shows a second cross-section of a combined machine according to the invention for producing annular parts.

FIG. 5 shows a longitudinal section of a combined machine according to the invention for producing annular parts.

FIG. 6 shows a schematic illustration of a coil having the coil starting piece and the coil end piece.

FIG. 7 shows an annular workpiece produced by means of a combined machine according to the invention.

FIG. 1 shows the production of annular parts according to the prior art in a schematic illustration. Thin metal sheet is fed in the form of a coil 7 from a decoiler 1 to the cutting machine 2, where the metal sheet 10 is cut to the required starting dimension. Then a mechanical and/or thermal rolling process is applied to the metal sheet 10 in one or more steps in a rolling machine 3 so that an annular open workpiece 34 having two longitudinal edges 29 a, 29 b is obtained, which longitudinal edges are then welded together by means of a weld seam 36 in a welding machine 4, whereby an annular part 35 is obtained, which is optionally processed further in an additional processing step by means of an expanding machine 5.

FIG. 2 shows, again in a schematic illustration, the inventive production of annular parts. Thin metal sheet having a thickness in the range of 0.4 mm to 1 mm is continuously fed in the form of a coil 7 from a decoiler 1 to the combined machine 9 as a starting material, wherein the workpiece, in one and the same combined machine 9, is fed by means of a roller mechanism, clamped, conveyed, cut to the required starting dimension, formed into an annular or cylindrical part on a rotating rolling machine, and welded and thus provided with a longitudinal seam 36.

Then the annular part 35 is automatically or manually removed from the combined machine 9 by means of a mechanism. In this method, further processing can optionally occur in an expanding machine 5 in an additional work step.

Instead of the feeding of the starting material from a coil 7, the feeding of pre-cut plates 8 is also mentioned as an alternative.

FIG. 3 shows a cross-section of the combined machine 9 according to the invention for producing annular parts 35, wherein the workpiece 16 is automatically fed in a conveying direction F of the combined machine 9 and is conveyed by means of the guiding rollers 19 a and the

-   roller guides 18 a, 18 b and by means of the -   advancing rollers 19 b through the clamping device 22 to beyond the     advancing roller 15. The coil starting piece 27 generally has a     non-straight edge 30 unsuitable for optimal welding and is therefore     fastened by means of the clamping device 22 and cut off by means of     the cutting head 24 integrated in the carrier 17 and deposited in a     scrap bin 11 a, 11 b, or conveyed out of the machine by means of a     flap 20, wherein a straight welding edge 29 a is obtained on the     first good piece 31 by means of the cutting. In a next process step,     the workpiece 16 is conveyed further onto the rolling tool 21 up to     the retaining device 14 at the end of the rotatable magnet bar 13     after the clamping device 22 has been opened, wherein the front end     of the workpiece 16 is retained by means of the retaining device 14     by pneumatic and/or magnetic application of force and is conveyed     further by means of the rolling tool 21, which rotates in a     direction of rotation R.

FIG. 4 shows, in a further cross-section, a combined machine 9 according to the invention, wherein the workpiece 16 has been conveyed further by a half rotation in the

-   direction of rotation R in comparison with the position shown in     FIG. 3 and has an approximately semicircular cross-section. By     continuous conveying of the workpiece 16 in the -   conveying direction F, a further half rotation in the -   direction of rotation R occurs so that the workpiece 16 has the     desired periphery and then can be fastened in such a way, by     applying a force by means of the clamping device 22, that the     rolled, slightly elliptical workpiece 34 can be severed from the     coil 7 by means of the cutting head 24, two straight welding edges     29 a, 29 b thus being formed and a gap B thus being formed. After     the can B between the two welding edges 29 a, 29 b is closed except     for a. small remaining gap by means of a further small rotation in     the direction of rotation R, wherein the workpiece 34 having a     slightly elliptical cross-section is deformed into an annular     workpiece 35 having a circular cross-section and then is fixed by     means of the clamping device 22, whereupon the application of force     at the retaining device 14 can be reduced or eliminated. In the     subsequent welding process, the two straight welding edges 29 a, 29     b are firmly joined by means by means of a longitudinal-seam weld,     and the annular workpiece 35 can then be removed from the combined     machine 9 by means of a removal mechanism not shown.

FIG. 5 shows the carrier 17 of the combined machine according to the invention, which carrier has an integrated cutting and welding device, in a longitudinal section, wherein the source 23, preferably a laser source, is switchable, so that the source is mechanically and electrically connected either to the cutting head 24, which can be moved in a

-   transverse direction Q, or to the welding head 25, which can     likewise be moved in the transverse direction Q, and is additionally     designed with a feed 26 for filler material for the purpose of     filling the remaining gap arising when two edges are joined with     filler material if necessary during the welding and thus closing the     remaining gap, whereby an optimal weld seam can be produced. The     workpiece 16 is guided between the upper and the lower part of the     clamping device 22, wherein the mismatch rollers 12 are used to     compensate a possible perpendicularly arising mismatch of the two     edges of the workpiece 16 to be welded together and thus to enable     an additional increase in the welding quality.

FIG. 6 shows, in a schematic illustration, a coil 7, from which the coil starting piece 27, which has a non-straight edge 30, was cut off in a first processing step and from which a first good piece 31 having the straight welding edges 29 a, 29 b was cut off in a second process step. Furthermore, the coil end piece 28 having the non-straight edge 30, and the last good piece 32 of the coil 7 and the next to last good piece 33 each having the two straight welding edges 29 a, 29 b, are illustrated.

FIG. 7 shows a slightly elliptical workpiece 34 produced in the combined machine 9 by means of the innovative method, after the cutting and rolling but before the welding, and an annular part 35 after the cutting, rolling, and welding, to which the longitudinally welded weld seam 36 has been applied. 

1. A method for processing thin steel strip, which is preferably but not exclusively continuously fed from a coil and which has a thickness in the range of preferably 0.4 mm to 1 mm, into workpieces, particularly for roll-bending substantially flat, sheet-shaped starting material into substantially tubular or annular objects such as drums or other preferably cylindrical objects or the like, the processing process being influenced and monitored by at least one operator from at least one operating station onward and the workpiece being continuously conveyed from a coil by means of an electronic control unit, being first fed to a straightening tool and then being processed further in a combined machine in at least three further process steps, a rolling process being applied to the workpiece in a first processing step, in that the workpiece is fixed by a retaining device under the application of force and continuously conveyed by means of a rotatable rolling tool until the full peripheral length has been reached, after a straight welding edge has been created by cutting off the coil starting piece, which is deposited in the at least one scrap bin, and a cutting process being applied to the workpiece in a second processing step, whereby two straight welding edges are produced at the interface, and a welding process being applied to the workpiece in a third processing step, a first welding edge and a second welding edge being welded to each other in such a way that an annular part having a weld seam is produced, and the annular part being ejected from the combined machine by means of a removal mechanism or being manually removed, characterized in that the three steps for processing the workpiece, the cutting in the cutting machine and the rolling in the rolling machine and the welding in the welding machine, are performed by means of the same equipment in a combined machine.
 2. The method according to claim 1, characterized in that the cutting and the welding in the combined machine occur preferably by means of a laser method or by means of a plasma method.
 3. The method according to claims 1, characterized in that the welding head and the cutting head are arranged on the same gantry on a carrier, wherein the welding head and the cutting head each can be moved in a horizontal direction and a vertical direction.
 4. The method according to claim 3, characterized in that the cutting and the welding occur by means of a combined head.
 5. The method according to claim 1 characterized in that, at least if a laser method is used, the welding head and the cutting head use one and the same source, preferably but not exclusively a laser source.
 6. The method according to claim 1 characterized in that the welding occurs with or without a feed of filler material.
 7. The method according to claim 1, characterized in that the coil starting piece of the coil, which is obtained when the cutting is performed for the first time, is deposited in a first scrap bin and the coil end piece of the coil, which is obtained when the cutting is performed for the last time, is deposited in a second scrap bin.
 8. The method according to claim 1, characterized in that the welding edges have, for example but not exclusively, a saw-tooth shape or wave shape.
 9. The method according to claim 1, characterized in that the sheet-shaped starting material is not continuously unrolled from a coil, but rather is cut into plates after a preceding cutting process and is fed in the form of pre-cut plates to the further processing by means of an individual sheet feed.
 10. A use of the method according to claim 1, for producing drums for a washing machine or a dishwasher or the like. 